My Gigabyte P35-DQ6 does have what you say is voffset, but is has NO vdroop from idle to load. I believe this is because it has a far superior power delivery system. I don't have an instrument to tell me any differences that may happen in nano-seconds on the voltage, but overall, it never seems to change. This would be consistant with a high quality board. So why do you say its a feature ? I can see how a mfg may undervolt to not go over recommended vcore for non-overclocked cpu's, but if I didn't overclock, my board wouldn't have vdroop either.

Its just cheap motherboards, not a "feature". If I am wrong, please test a DQ6 and show the results. Reply

Considering the heat produced I can't see a justification for the idea of drastic shifts in the cooling industry. Realistically there aren't THAT many overclockers using water cooling at all and current (including older) processors having lower power consumption were what brought the cooling industry to what it is today.

You may say past some point the heat isn't the factor, but you still need a decent heatsink up until that point. 100W of heat for example is a non-trivial level even though some past parts have exceeded that. Reply

What I really meant to say is that it's not just a matter of getting rid of the heat but doing so without the system sounding like it has a leaf blower hidden inside, and for that many lesser heatsinks just don't cut it. Reply

What I really meant to say is that it's not just a matter of getting rid of the heat but doing so without the system sounding like it has a leaf blower hidden inside and for that many lesser heatsinks just don't cut it. Reply

What I really meant to say is that it's not just a matter of getting rid of the heat but doing so without the system sounding like it has a leaf-blower hidden inside and for that many lesser heatsinks just don't cut it. Reply

This was the exact type of article I love to sit down and read through. It doesn't matter if portions of it are above my head, it just gets me to rise up another level to grab at them. Your article was a great read and I very much hope to see many more like this one in the future!

Regarding the P5E3, I am somewhat surprised that 0.81v was the lowest you could set. Even the budget board P31-DS3L offers 0.51v as an option, my personal P35-DQ6 has 0.50v as a vCore option. I found your commentary regarding Load Line Calibration to be illuminating... this is exactly what enthusiasts like myself and others need to know.

Lastly, I hate to ask here but Google was no help, Intel's ARK database didn't cover it, and Intel's datasheet didn't mention that I could see... what exactly is P35's process size and default vCore? The same as X38's...? As much as I love Gigabyte they are notorious for their lack of system voltage info... Reply

The P35 and X38 chipsets are both made using Intel's standard 90nm process technology. It's not uncommon for chipset's to lag behind current CPU offerings by a whole process generation or more. With that being said, Intel's upcoming P45 chipset, the last of it's kind (recall that all future CPU technologies will make use of an onboard memory controllers) will be made on the 65nm process -- something even the X48 won't have. In fact, this reduction in process size may have considerable benefits for P45 when it comes to the reduction in power consumption and increased performance headroom, particularlly when overclocking. The P45 default Vmch is 1.15V, X38 is slightly higer at 1.25V. Based on this I would expect to see the P45 come in around 1.05V or possibly even lower. Reply

Kris, great article. But, when did $400-500 worth of watercooling equipment become so commonplace, as to be putting the one (or is that two?) companies who make phase-change units out of business? If freon is no longer needed for extreme CPU cooling, couldn't Vapochill just start making even more expensive, higher-end watercooling? Reply

The documentation accompanying the BIOS settings of almost all enthusiast motherboards is frequently obscure and incomplete - probably because it is printed many months before the board/BIOS is released, plus the leading manufacturers never bother to update BIOS user-documentation when they update the BIOS. Also, it does seem that the documentation authors have a uniformly poor grasp of the English language and prefer to keep descriptions of all BIOS settings as vague and incomprehensible as possible. It is also so common to find sundry BIOS entries not documented AT ALL anywhere in the motherboard manual, even the (so-called) latest on-line version.

So I have a request on behalf of those like myself desperately trying to understand each entry in the BIOS of that brand-new and very expensive enthusiastic motherboard that I have just purchased, with that abysmal so-called user-manual and pathetic in-BIOS "Help" Function-key :-

Would it be possible for you or other at Anandtech to fully document/explain all the terms used in the text of the CPU and memory BIOS settings of the most popular enthusiast motherboards?
To keep such an exercise manageable, I suggest confining the exercise initially to existing and upcoming enthusiast desktop motherboards that are fully compatible with Penryn and Phenom. At present, X48, nVidia 780i, AMD 790FX..... Reply

Thank you very much for this great article. What a wonderful Christmas gift from Anandtech! This is one the most complete article I have ever read. CPU performance, overclocking, mobo settings, power consumption all in one article. What a joy to read. Reply

Thank you for the detailed information. One has to be a little nervous however for the implications in what your work has found. Will Intel's improvements in refining 45nm technology push the line or has it been drawn in the sand?? Reply

This is a great article from both a readability and technical standpoint, I found it very enjoyable to actually read the commentary, which I cannot say is true for 95% of tech reviews. Also the graphs and information presented were extremely useful. I love the demystifying of the vdroop issue to prove that it's a GOOD thing. Reply

Finally a review with some understandable explanations of Bios settings and there realation ships. As the motherboards change you get new Bios names for things and your eyes glaze over wondering what the heck some of the terms mean. Look forward to future articles of popular motherboards Bioses. I will be printing this article out. Thanks much Reply

Finally a review with some understandable explanations of Bios settings and there realation ships. As the motherboards change you get new Bios names for things and your eyes glaze over wondering what the heck some of the terms mean. Look forward to future articles of popular motherboards Bioses. I will be printing this article out. Thanks much Reply

So lets say I have a 65nm Core Duo running between 0.850V-1.3525V. These are the product specs, which I guess .850 is the low limit and 1.325 is the high limit. Why does the voltage have to decrease depending on load? Is it just as simple as "supply and demand"? How does running the CPU at 1.352v run the risk of instability? Reply

Great article. You guys have really been distinguishing yourselves with in-depth work on overclocking the last few months: exploring obscure bios settings, tinkering with "extreme" cooling -- keep it up!

My experience with a qx9650 so far is very similar to yours: easy scaling to 4 ghz, difficult scaling after that with 4.2 ghz being the practical max for regular operation (folding, etc.).

One issue I will be interested to see you address in the future is fsb overclocking on yorkfield. So far I am seeing yorkfield top out at lower fsb (450-460) than was possible for kentsfield on a comparable P35 or X38 platform. That is not so significant for the unlocked Extreme Edition chips, but could make it difficult to achieve the magic 4 ghz with the q9550 and especially the q9450. Reply

Great article. You guys have really been distinguishing yourselves with in-depth work on overclocking the last few months: exploring obscure bios settings, tinkering with "extreme" cooling -- keep it up!

My experience with a qx9650 so far is very similar to yours: easy scaling to 4 ghz, difficult scaling after that with 4.2 ghz being the practical max for regular operation (folding, etc.).

One issue I will be interested to see you address in the future is fsb overclocking on yorkfield. So far I am seeing yorkfield top out at lower fsb (450-460) than was possible for kentsfield on a comparable P35 or X38 platform. That is not so significant for the unlocked Extreme Edition chips, but could make it difficult to achieve the magic 4 ghz with the q9550 and especially the q9450. Reply

Great article. You guys have really been distinguishing yourselves with in-depth work on overclocking the last few months: exploring obscure bios settings, tinkering with "extreme" cooling -- keep it up!

My experience with a qx9650 so far is very similar to yours: easy scaling to 4 ghz, difficult scaling after that with 4.2 ghz being the practical max for regular operation (folding, etc.).

One issue I will be interested to see you address in the future is fsb overclocking on yorkfield. So far I am seeing yorkfield top out at lower fsb (450-460) than was possible for kentsfield on a comparable P35 or X38 platform. That is not so significant for the unlocked Extreme Edition chips, but could make it difficult to achieve the magic 4 ghz with the q9550 and especially the q9450. Reply

It seems that ATI cards have less of a drop going from XP to Vista (down to zero and even negative sometimes). It might be instructive to use that for the charts that compare Vista to XP for 3D (e.g., the 3Dmark06 benchmark). Reply

Capacitors have their capacitance turned into reactance at higher frequencies. Anything that qualifies, in a circuit, as a capacitor, such as two wires riding in parallel, will have, to a greater or lesser extent, the same problem in the design.

Reactance rolls off high frequencies. More power is required to offset that.

This is the same problem whether dealing with low frequencies in an audio circuit (where it may be less of a problem), or a high performing computer. It's almost impossible to eliminate all stray capacitance from a circuit, and more circuitry becomes capacitive at higher frequencies. This will only increase as a problem as we get to smaller processes, such as 32nm. Reply

Very impressive. Seems more like a thesis paper than a typical tech site article. While the content on AT is of a higher quality than the rest of the sites out there, I think the other authors, founder included, could learn a thing or two from an article like this. Less commentary/controversy and more quality is the way to go. Reply

"Do they worry more about the $5000-$10000 per month (or more) spent on the employee using a workstation, or the $10-$30 spent on the power for the workstation? The greater concern is often whether or not a given location has the capacity to power the workstations, not how much the power will cost."

For High Performance Computers (HPC a.k.a. supercomputers) every little bit helps. We are not only concerned about the power from the CPU, but also the power from the little 5 Watt Ethernet port that goes unused, but consumes power. When you are talking about HPC systems, they now scale into the tens-of-thousands of CPUs. That 5 Watt Ethernet port is now a 50 KWatt problem just from the additional power required. That Problem now has to be cooled as well. More cooling requires more power. Now can your infrastructure handle the power and cooling load, or does it need to be upgraded?

This is somewhat of a straw-man argument since most (but not all) HPC vendors know about the problem. Most HPC vendors do not include items on their systems that are not used. They know that if they want to stay in the race with their competitors that they have to meet or exceed performance benchmarks. Those performance benchmarks not only include how fast it can execute software, but also how much power and cooling and (can you guess it?) noise.

In 2005, we started looking at what it would take to house our 2009 HPC system. In 2007, we started upgrades to be able to handle the power and cooling needed. The local power company loves us, even though they have to increase their power substation.

Thought for the day:
How many car batteries does it take to make a UPS for a HPC system with tens-of-thousands of CPUs? Reply

this is a great article - very technical, will have to read it step by step to get it all ;-)

but i have one question that remains for me.. how is it about electromigration with the very filigran 45nm structures? we have here new materials like the hafnium based high-k dielectricum, guess this may improove the resistance agains em... but how far may we really push this cpu until we risk very short life and destruction? intel gives a headroom until max 1.3625V .. well what can i risk to give with a good waterchill? how far can i go?

i mean feeding a 45nm core p.ex. 1,5V is the same as giving a 65nm 1,6375! would you do that to your Q6600? Reply

Electromigration is an effect usually seen in the interconnect, not in the gate stack. It occurs when a wire (or material) has a high enough current density that the atoms actually move, leading to an open circuit, or in some cases, a short.

To address your questions:
1. The high-k dielectric in the gate stack has no effect on the resistance of the interconnect
2. The finer features of wires on a 45nm process do have a lower threshold to electromigration effects, ie smaller wires have a lower current density they can tolerate before breaking.
3. The effects of electromigration are fairly well understood at this point, there are all kinds of automated checks built in to the design tools before tapeout as well as very robust reliability tests performed on the chips prior to volume production to catch these types of reliability issues.
4. The voltage a chip can tolerate is limited by a number of factors. Ignoring breakdown voltages and other effects limited by the physics of transistor operation, heat is where most OC'ers are concerned. As power dissipation is most crudely though of in terms of CVf^2 (capacitance times voltage times frequency-squared), the reduced capacitance in the gate due to the high-k dielectric does dramatically lower power power dissipation, and is well cited. The other main component in modern CPU's is the leakage, which again is helped by the high-k dielectric. So you should expect to be able to hit a bit higher voltage before hitting a thermal envelope limitation. However, the actual voltage it can tolerate is going to depend on the CPU and what corner of the process it came from. In all, there's no general guideline for what is "safe". Of course, anything over the recommended isn't "safe", but the only way you'll find out, unfortunately, is trial and error. Reply

Doh! Just noticed my own mistake:
high-k dielectric does not reduce capacitance! Quite the contrary, a high-k dielectric will have higher capacitance if the thickness is kept constant. Don't know what I was thinking.

Regardless, the capacitance of the gate stack is a factor, as the article mentioned. I don't know how the cap of Intel's 45nm gate compares with that of their 65nm gate, but I would venture it is lower:

1. The area of the FET's is smaller, so less W*L parallel plate cap.
2. The thickness of the dielectric was increased. Usually this decreases cap, but the addition of high-k counter acts that. Hard to say what balance was actually achieved.

Asking how much voltage can be safetly applied to a (45nm) CPU is a lot like asking which story of a building can you jump from without the risk of breaking both legs on the landing. There's inherent risk in exceeding the manufacturer's specification at all and if you asked Intel what they thought I know exactly what they would say -- 1.3625V (or whatever the maximum rated VID value is). The fact of the matter is that choices like these can only be made by you. Personally, I feel exceeding about 1.4V with a quad 45nm CPU is a lot like beating your head against a wall, especially if your main concern is stability. My recommendation is that you stay below this value, assuming you have adequate cooling and can keep your core temperatures in check. Reply

Granted, that's undervolted, at stock voltage it would be more like 70W instead of 54W :-).
I think the criticism of intel's TDP was justified in P4 days, which really did exceed their TDP under high load. Nowadays, the TDP (at least the numbers from intel) is pretty meaningless to the end-user, since cpus with very different actual power consumption have the same rating (QX6850 and QX9650 for example...), but at least all of their cpus actually stay below the TDP. Reply

For someone like me who's fairly new to OC-ing and has been struggling to find a technical and pragmatic introductory guide to the skill, this article is like gold-dust! I look forward to the New Year when I hope to finally remove my E6300 from its temporary ASRock housing and get some decent overclocking done :)

Yeah, the rest of Anand's staff should start thinking about securing their future. Spreading some false rumors about him visiting "Tom's Hardware" office would be a good start. Add to this a couple of sexual harassment accusations and you have a winning combination that would quickly finish his career.

Guys, let me spell it for you. If you don’t take action soon, you all will be F-I-R-E-D.
Reply